In the concrete industry, when building bridges, buildings, roads and the like, it is often necessary to pour large horizontal slabs of concrete. Once poured, it is usually necessary to machine the slab. Such machining may include cutting seams completely through the slab to form expansion joints and to allow for foundation shifting, cutting notches partially into the slab at predetermined locations at which stress cracks will form along the slab, cutting multiple grooves into the slab to create a high friction surface such as for bridges, grinding the surface of the slab and the like. While performing a cut, the operator controls the direction, cutting speed, cutting depth and the like. Concrete saws are also used in the demolition or removal of concrete, such as during the sawing and replacement of bridge decks. Various types of concrete saws may be utilized to carry out these machining and demolition tasks. In larger industrial applications, large self-propelled saws are used that are powered in a variety of manners, such as by gasoline, diesel, electric, propane and natural gas engines mounted on the saw. Concrete saws that are powered by an internal combustion engine, or that are electrically powered and include an internal combustion engine generator, cannot be used indoors due to the exhaust generated by the engine.
In conventional electric concrete saws used for indoor cutting of concrete, a single powerful electric motor is used for all electrical power requirements for these large and heavy saws. For example, a single electric motor supplies power for all aspects of the electric concrete saw, including for rotating the saw blade, for raising and lowering the saw blade, and for powering the wheels of the saw to assist in moving the concrete saw from one location to another. Such electric motors are large and powerful, often exceeding an output of 10 horse power (HP) and requiring 400 volts or more to operate. Such motors require an external power supply and cannot be plugged into a typical 120 volt outlet present in most residential structures. Such heavy duty motors used in concrete saws are often three-phase motors, which require a special connection to three-phase electric power supply typically provided to industrial and other non-residential buildings.
Three-phase power supplies are not always readily accessible for connection to the motor at all areas of a worksite. Therefore, before the electric motor is connected to an external three-phase electric power supply, the wheels of conventional electric concrete saws are not self-propelled. For example, before connection to a power supply, an operator must move the saw from a delivery location (e.g. from a truck, trailer, or other vehicle) to a cutting location (e.g. inside a building) without assistance from the electric motor. Movement of these large and heavy industrial electric concrete saws is difficult and laborious without assistance from the motor to propel the wheels. Often more than one operator is needed to maneuver the machine from one location to another. Further, connecting the saw to an external three-phase electric power supply to make the saw self-propelled, and to thereby assist in moving the saws, is often impractical or impossible in many locations.